There is disclosed a housing structure in which, for example, as shown in FIG. 8, hollow steel members are used for major welding framework steel members to which L-shaped steel members in cross section and channel-shaped steel members in cross section are combined, as a technique for a conventional switchgear taking into account quake resistant performance. More specifically, height directional hollow steel members 41, width directional hollow steel members 42, and depth directional hollow steel members 43 are combined with L-shaped foundation steel members in cross section 44 arranged in the depth direction of a foundation portion of the housing; and further, these members are appropriately combined with channel-shaped steel members in cross section and the whole is welded and joined to form a framework of the housing, thereby achieving an improvement in rigidity. Welding panels 45 are attached to outer surfaces (for example, see, Patent Document 1).